The Sony SRF-M100 is an FM Stereo/AM PLL Synthesized Receiver, designed for portable use and offering a range of features for radio listening, timekeeping, and personal reminders.
Function Description:
The SRF-M100 serves primarily as a portable radio receiver, capable of tuning into both FM stereo and AM bands. Its PLL (Phase-Locked Loop) synthesized tuning ensures stable and accurate frequency reception. Beyond basic radio functions, the device incorporates a clock, a timer, and an alarm, allowing users to set reminders or wake up to the radio or a beep sound. The unit features a built-in speaker for monaural listening and a stereo earphone jack for private, stereo sound. The earphone cord also doubles as the FM antenna, enhancing portability.
Important Technical Specifications:
- Frequency Range:
- FM: 87.5 – 108 MHz (with a channel step of 0.05 MHz, though the display shows 0.1 MHz steps)
- AM: 531 – 1602 kHz (with a channel step of 9 kHz)
- IF (Intermediate Frequency):
- Speaker:
- Size: 4.4 cm (1 3/4 inches)
- Impedance: 7.2 ohms
- Output:
- Stereo earphones jack (stereo ø 3.5mm, load impedance 16 ohms)
- Power Output:
- 80 mW (at 10% harmonic distortion)
- Power Requirements:
- 3 V DC, two R6 (size AA) batteries
- Battery Life (using Sony SUM-3 (NS) batteries):
- Earphones: FM approx. 35 hours, AM approx. 45 hours
- Speaker: FM approx. 22 hours, AM approx. 26 hours
- Dimensions:
- Approx. 121 x 72 x 27 mm (w/h/d) (4 7/8 x 2 7/8 x 1 1/8 inches) including projecting parts and controls
- Mass:
- Approx. 198 g (7.0 oz.) including batteries
- Supplied Accessory:
Usage Features:
- Display Window: A clear display shows the frequency, time, and various indicators (STEREO, Battery, Alarm, Timer, Frequency, Band, PRESET, preset number).
- Tuning: Users can tune in to desired stations by pressing TUNE/TIME SET + or - buttons. Keeping the button pressed allows for rapid frequency changes.
- Preset Tuning: The radio allows for storing up to 7 stations for each of the FM and AM bands, enabling quick access to favorite stations. The process involves tuning to a station, pressing and holding ENTER/CLOCK, selecting a preset number, and confirming with ENTER/CLOCK.
- Band Selection: A BAND selector switch allows switching between FM and AM bands.
- Volume Control: A rotary VOLUME control adjusts the listening level.
- AUTO OFF/POWER Switch: This slide switch turns the radio on and off. It also features an auto-off function that turns the radio off after approximately 90 minutes to conserve battery life.
- STEREO/MONO Selector: This switch allows users to choose between stereo and monaural reception for FM programs. While earphones provide stereo sound, the speaker provides monaural sound. If an FM stereo program is noisy due to a weak signal, switching to MONO can improve sound quality, albeit without the stereo effect.
- Antenna: The telescopic antenna is used for AM reception and should be extended and adjusted for optimal FM reception. The earphone cord also functions as the FM antenna.
- Clock Setting: The device includes a clock that can be set to the current time, with options for 12-hour (AM/PM) or 24-hour display.
- Timer Function: Users can set a timer to sound a beep through the speaker or earphones after a specified period (1 to 180 minutes). This is useful for reminders.
- Alarm Function: An alarm can be set to sound a beep at a desired time.
- Battery Indicator: A battery indicator flashes in the display window when batteries are weak, prompting replacement.
Maintenance Features:
- Battery Replacement: The device uses two R6 (size AA) batteries. Instructions are provided for correct insertion and replacement. It is recommended to replace both batteries with new ones when the indicator flashes.
- Battery Care: Users are advised not to mix new and used batteries, not to attempt to charge the batteries, and to remove batteries if the unit will not be used for a long time to prevent damage from leakage.
- Flexible Circuit Board Repairing: Specific guidelines are given for repairing flexible circuit boards, including maintaining a soldering iron temperature around 270°C, avoiding repeated contact with the same conductor, and being careful not to apply force during soldering/unsoldering.
- Chip Component Replacement: Instructions emphasize not reusing disconnected chip components and being aware that the minus side of a tantalum capacitor may be damaged by heat.
- Electrical Adjustments: Detailed procedures are outlined for AM IF adjustment, AM frequency coverage adjustment, AM tracking adjustment, FM frequency coverage and taking adjustment, FM tracking adjustment, and FM VCO adjustment. These adjustments involve using specific test equipment like RF signal generators, VTVMs, and frequency counters to ensure optimal performance across the frequency bands.
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